Liquid or gas filtration in the 1 to 20 micron range is currently performed primarily by using disposable filter media. While filter media of this type provides acceptable filtration performance, it does so at high cost. The filter media itself is costly, due in part to the need for frequent replacement of the media. Disposal of spent media also presents a problem, since federal authorities consider most of the spent media to be hazardous waste and therefore subject to regulations for hazardous waste disposal.
Regenerable filter media in the form of metallic wire filters and sintered powder filters are also used. These are random pore filters, however, and regeneration is never complete since backflushing invariably leaves a certain amount of trapped contaminant within the media.